With the increase in manufacture and use of water-based surface coatings having in stable suspension film-forming latex binders (such as those in conventional latex paints) and structurally ionic film-forming resinous binders (such as those used as interior linings of beverage cans, various coatings for metal, etc.), the problems of clarifying the aqueous phase of such wastes and of converting the dispersed resinous solids into a material that is reasonably satisfactory for landfill or other disposal have become significant.
Conventional flocculation of binder latices, typically as practiced with various polymeric and inorganic flocculants, can be done. However, such practice has been ineffective for handling, in a manner acceptable to environmental authorities, the disposal problems that arise from water containing the usually quite small particle, water-dispersible, structurally ionic coating binders.
The instant flocculation process is to be distinguished from related prior art proposals exemplified by Chappell, U.S. Pat. No. 4,116,705; Kupiec and Escher, U.S. Pat. No. 4,149,968 and by Uchikawa and Shimoda, U.S. Pat. No. 3,947,283. These can be characterized as "cementation" or "concretion" processes wherein the entire aqueous waste solidifies as a concrete-like mass having a total volume many times that of the suspended and/or dissolved waste. In essence, then, it is evident that such prior art processes convert substantially all of the water in the aqueous waste to a solid product. In contrast, the instant process provides for a distinct separation of clarified effluent on the one hand, and, on the other, waste solids in a compact and practical form.
The present process, therefore, comes as a pleasant surprise because it not only efficiently and effectively can be used to treat aqueous wastes containing either structurally ionic resins or those that are nonionic or partially so, but it also can be used to treat them in a way that can satisfy today's critical authorities concerned about both clarification of the water effluent and disposal of the solid fraction of such wastes.